THE STOMACH AND ITS DIGESTION ROLE

The stomach and its role in digestion

The stomach is a muscular sac that lies between theesophagus and thesmall intestine in the upper abdomen. The stomach is not the only part of your digestive system that absorbs food but rather is a part of the digestive system and important for churning food into a consistency that is easier to digest for the rest of your intestines.

Function of the stomach

• The stomach is J-shaped and it can expand to temporarily store food.
• Partial digestion of the food takes place here. The churning action of the stomach muscles physically breaks down the food.
• The stomach releases acids and enzymes for the chemical breakdown of food. The enzyme pepsin is responsible for protein breakdown.
• The stomach releases food into the small intestine in a controlled and regulated manner.

Chewed food passes from the esophagus into the stomach; the flow is somewhat regulated by the esophageal sphincter but more importantly depends on how fast you eat and if you are eating both solids and liquids. The passage of food from the stomach to the small intestine is controlled by the pyloric sphincter. The crushed and mixed food is liquefied to form chyme and is pushed through the pyloric canal into the small intestine.

A network of blood vessels and nerves surrounds the stomach; this is responsible for the regulation of the secretion and the motion of stomach muscles that churns food.

Laparoscopic view of the stomach

The photo demonstrates the laparoscopic view of the stomach during the early stages of a sleeve gastrectomy operation. The stomach is a rather larger organ with a redundant blood and nerve supply. The two tan organs at the top of the picture are the liver on the left and the spleen on the right. The picture demonstrates the J shape of the stomach. The large blood vessels and the abrupt turn of the stomach on the left side represent the area known as both the angular incisure or incisura angularis.

Different parts of the stomach

The stomach can be divided into four distinct parts. These are the cardia, fundus, corpus, and pylorus.

The cardia is the first portion of the stomach and is where food content passes from the esophagus into the stomach. The acids and enzymes referred to as the gastric juices are manufactured in the cardia. The fundus stores undigested food and also the gases released from the chemical digestion of food. The body of the stomach or the corpus is the largest of the four parts that make up the stomach. And this is where the bulk of the partial digestion occurs. The pylorus is connected to the duodenum or the beginning of the small intestine. The contents of the stomach move into the small intestine via the pyloric canal.

The stomach wall

The walls of the stomach consist of four layers, similar to other parts of the gastrointestinal tract. These layers, starting from the innermost layer, are named mucosa, sub-mucosa, muscularis externa, and the serosa.

The mucosa consists mainly of the gastric glands that secrete the digestive juices. It is covered by a layer of columnar epithelial tissue. The sub-mucosa consists of dense connective tissue and has blood vessels, lymphatic vessels, and nerves running through it. The sub-mucosa supports the mucosa and allows it to move in a flexible manner during peristalsis.

Peristalsis is the contraction and relaxation of the stomach muscles to physically breakdown food and propel it forward. These contractions are created by the muscular wall of the stomach which consists of inner circular and outer longitudinal smooth muscle. The outermost layer of the stomach wall, the serosa consists of an epithelial layer and connective tissue which connects to the surrounding organs. The mucosa and the sub-mucosa are present as folds termed rugae. When the stomach is distended with food, the rugae are flattened out and appear smooth.

Cell types in the stomach that help with digestion

There are four main types of cells for stomach secretions spread all over the inner surface of the stomach:

• Mucous cells secrete the alkaline mucous for shielding the epithelium from hydrochloric acid. These are found in the fundic, cardiac, and pyloric region.
• Parietal cells, located in the fundic, cardiac, and pyloric region, secrete hydrochloric acid; the acid activates release of pepsin for protein digestion. The acid also kills micro-organisms swallowed with the food.
• Chief cells secrete pepsin. These cells are located in the fundic region.
• G cells are found in the fundic, pyloric, and gastric region. These secrete gastrin which stimulates the secretion of hydrochloric acid.

Healthy habits for a healthy stomach

Certain lifestyle habits can help you maintain stomach health and also counter abdominal obesity. If you notice that certain food types do not agree with you, try to keep away from them. Limit junk food. If you experience bouts of acidity, consider adding to your diet food items that are alkaline in nature. Take walks, it aids digestion, will help you shed calories, and prevent a condition like GERD from occurring. In fact, a sedentary lifestyle with little or no exercise contributes to stomach-related problems.

Some stomach conditions and diseases

The umbrella term for stomach disease is gastropathy. Some common stomach disorders include:

• Dyspepsia: This is a condition characterized by a feeling of fullness; indigestion; and pain in the upper abdomen or lower chest. Other symptoms include nausea and vomiting. Dyspepsia can be a precursor to GERD and may also indicate angina.
• GERD: Gastroesophageal reflux disease is a condition in which the stomach acids rise up the esophageal passage. Heartburn is a common symptom of the condition.
• Peptic Ulcers – These can occur when the protective mucous lining of the stomach walls is damaged by the stomach acids. The bacterium, Helicobacter pylori is thought to be an important factor in the development of gastric and duodenal ulcers.

Anatomical Structure: 

Stomach

Speciality Classification: 

Surgical

Medical Entity Classification: 

MedicalCode

MeSH Identifier: 

A03.556.875.875

National Library of Medicine: 

MeSH

Medical Audience: 

Patient

Tools for Minimally Invasive Surgery

Laparoscope

 
Surgical scopes are among the oldest forms of medical instrument, with some of the earliest examples on record dating back to 70AD. Initially consisting of simple hollow tubes, over time these rudimentary devices were adapted to include magnifying lenses and illumination, eventually evolving into the sophisticated surgical scopes used today. Once the image has been digitized, it may undergo additional processing, with some systems offering features such as filtering, noise reduction, color adjustment and image enhancement. The resulting video feed is then sent to a monitor, where it can be viewed by the surgeon and the rest of the surgical team. 

Needle Driver

 
Needle drivers, or needle holders, are used to grasp and manipulate needles to enable free-hand suturing of wounds or surgical incisions within the body during laparoscopic procedures. Laparoscopic needle drivers typically comprise a long narrow shaft, with a handle at one end and a set of hinged jaws at the other. The shaft is made of surgical steel with an outer layer of non-conductive plastic or silicone. Jaws are generally made of tungsten carbide and may have additional coatings applied to improve grip.

Trocar

 
In its simplest form, a trocar is a pen-shaped instrument with a sharp triangular point at one end, typically used inside a hollow tube, known as a cannula or sleeve, to create an opening into the body through which the sleeve may be introduced, to provide an access port during surgery. Today, a very wide range of precision-engineered laparoscopic trocars exists, with instruments available in a variety of lengths and diameters, and with many different styles of tip. Most modern trocars comprise an outer housing assembly, a sleeve that fits inside the housing assembly and a piercing stylus which slots into the sleeve such that the tip protrudes from the lower end of the instrument.

Grasper

 
Wielding bowel graspers requires practice and skill because the tips of the graspers are small and pressure at the tips is magnified; too much pressure can lead to tissue damage and too little pressure can cause the tissue to slip out of grasp. Minimally invasive techniques can deprive surgeons of the tactile feedback, depth perception and hand-eye co-ordination available to them during open procedures, making it much more difficult to judge how much force to apply. Bowel tissue is considered to be among the most delicate in the human body, so it is essential that the grasping tip is able to offer a safe, secure grip, without exerting excessive pressure.

Surgical Mesh

Mesh-like structures, woven from the suture materials of the day or formed from organic materials such as animal tendons, have been used in surgical repairs for more than a century.  However, it was not until the development of synthetic polymer mesh that such techniques were widely adopted. Meshes can be categorized in terms of weight, pore size, material, fiber type and flexibility. Heavyweight meshes tend to form a dense scar plate and are best suited to applications where mechanical stability is a factor. Lightweight meshes are formed from thin fibers and are designed to flex with normal physiological movement.

• Colon
  The colon has bacteria which helps break food down; it is shorter than the small intestine but has a larger diameter.
• Pancreas
  The pancreas is a gland that is a part of the digestive system as well as a hormone system that regulates sugar.
• Gallbladder
  The concentrated bile stored in the gallbladder is released when fatty foods enter the small intestine.